On Monday morning a new man will join the leadership of Britain's biggest police force. He will not wear a uniform, has never walked the beat, and lacks the power to arrest a sausage. But some argue he will be more powerful than Scotland Yard chief Bernard Hogan-Howe, since he can trigger the commissioner's removal from office.

The man is Kit Malthouse, the Conservative politician in charge of the Mayor's Office for Policing and Crime, which is now in charge of setting the strategy and budgets for Scotland Yard, and responsible for its performance. The all-party committee that oversaw policing in London is gone. The rest of the country will follow later this year, when their police authorities are abolished and they elect their own police and crime commissioners to oversee their local forces.

The radical idea, championed by the Conservatives as bringing more accountability, has been criticised by police chiefs who fear it will lead to a greater politicisation of policing in Britain.

London will lead the way. Mayor Boris Johnson has delegated his formal powers to Malthouse, a deputy mayor. Outside the capital the police and crime commissioner will be directly elected.

One of those close to ministerial thinking on the power shift, Blair Gibbs, from the thinktank Policy Exchange, said: "People who run the police, the deployments, operations and arrests, remain the chief constables. But the leader of the police, who is answerable to the public and sets the direction, is the [police and crime] commissioner or in London the mayor.

"The move to a single personality will make the accountability of the police more visible to the public and make it easier for them to hold that person to account."

It means that the professional judgment and experience of police chiefs is no longer front and centre. The elected politician will claim a democratic mandate to have their priorities implemented: policing will be either blessed by the politician's genius and feel for the public mood, or held hostage by their foibles and pandering to populism.

In London, Met commissioner Hogan-Howe, who will on Monday make his first big speech setting out his vision for "total policing", retains operational independence.

The Labour peer Lord Toby Harris says the success of the new structure will depend on how much the politicians want to wield their power. Harris is a former chair of the Met Police Authority, abolished to make way for "sheriff" Malthouse. "A lot of this is about how the personalities work together," says Harris. "If they have confidence in each other, it's not going to be a problem. If not, there will be fireworks."

Since winning the mayoral election in 2008, the Conservatives in London have showed they will exert their power over the police. One of their first acts was to oust the then commissioner Ian Blair, who left warning of the politicisation of the service. He was followed by Sir Paul Stephenson, who three years later resigned over the phone-hacking scandal.

With hindsight, Malthouse's only sin may have to have been too public about it, too soon.

Later that year Malthouse said politicians had always influenced or interfered with policing, but that he was just being more open about it: "Anyone who thinks that politicians have not been quietly involved with the police, or indeed that smart police officers have not been taking account of the views of politicians, is living in cloud cuckoo land."

Gibbs accepts policing priorities may well change according to the political views of the elected politician. So a Liberal Democrat in the south-west elected on a civil liberties platform may insist on less use of CCTV, while a Labour politician in north-west England may demand more.

In London, Boris Johnson was elected after promising more police on buses, so passengers felt safer. The police did not believe this warranted resources given what they saw as the priorities, but felt they had to comply. They also had to act when Malthouse demanded action over dangerous dogs, with one police source claiming the deputy mayor was on the phone regularly about the issue, and had confused the world-renowned crimefighters at Scotland Yard with dog catchers.

All this jockeying for position comes ahead of a fierce re-election battle for Johnson, and as the Met and other forces face swingeing budget cuts.

But there is a risk for politicians, warns Harris, who make big promises to cut crime, but are hostage to cyclical factors such as an economic downturn, or new gadgets driving up robbery, which neither they or police chiefs can control: "Boris takes over the Met and he is responsible for whatever happens, whether it is good or bad."